Research Highlights

Research Highlights
The Pigweed Awareness Campaign: Spreading the Word to Reduce the Spread

Palmer amaranth can spread to new fields in various ways including contaminated livestock feed. The weed is thriving in a Grant County, North Dakota pasture, deposited in the field from cattle manure. Many weed seeds remain viable through the cattle digestive process. Photo: Joe Ikley

By Carol Brown

Many farmers are knowledgeable about the weeds that grow in their crop fields and what to do about them. But there are others who don’t regularly deal with these pesky plants and may inadvertently create weed issues in crop fields. Joe Ikley, a North Dakota extension weed specialist, is working to change this.

Ikley is leading the Pigweed Awareness Campaign, a project supported by the North Dakota Soybean Council and the North Dakota Corn Utilization Council. This effort aims to inform farmers and others how problematic pigweed species are spread and how to reduce field infestations.

“Specific pigweeds like waterhemp have been problematic for farmers in North Dakota, and we have had several instances of Palmer amaranth arise via introduction or infestation,” Ikley says. “Through conversations with staff at these two commodity groups, I agreed to be the point person to get more information out regarding these weeds. We want to create awareness of how they are spread and how difficult it is to control them.”

Waterhemp, Palmer amaranth and other pigweeds can produce a multitude of seeds per plant. Herbicide resistance and weed escapes are problems that compound the challenge of their control. Ikley and other weed management experts are seeing additional ways these weeds are getting into fields beyond the traditional methods.

This 3D-printed, life-size Palmer amaranth plant can garner attention at trade shows and meetings. The model has been a conversation starter for Joe Ikley and his team of weed specialists to talk about how this noxious weed can spread in North Dakota. Photo: Joe Ikley

“A number of the Palmer amaranth infestations have originated from animal feed,” Ikley explains. “Those who raise livestock may not have been exposed to information about these pigweeds like crop farmers have. We want them to be aware of how animal operations could be part of the spread and how bad these weeds can be for crop production.”

For instance, livestock farmers may feed their cattle grain screenings, which is grain that has been docked due to reduced quality including shrunken or broken kernels and hulls, volunteer grain, chaff, and weed seeds. Varieties of pigweed seeds have been found in grain screenings. Also, if livestock is grazed and these weeds are present in the pasture, cattle may eat the weeds. The weed seeds pass through the animals into their manure, which is then spread onto fields as fertilizer. Many of those weed seeds stay viable throughout this process.

Additionally, Ikley and his research team have found Palmer amaranth in at least one source of contaminated grain screenings that is resistant to five herbicide modes of action including glyphosate (HRAC Group 9), atrazine (Group 5), ALS (Group 2) and HPPD (Group 27) inhibitors, as well as 2-4,D and dicamba (Group 4), making weed control quite difficult. 

A pre-emergence herbicide application with multiple active ingredients is a good start, he says. In his herbicide trials, he found a post-emergence application mix of glyphosate and dicamba was reasonably effective for waterhemp when applied at the appropriate time, when weed escapes were 1 to 2 inches tall. When the weeds are taller than 2 inches, they become harder to control.

The Pigweed Awareness Campaign is providing this information to livestock farmers and others who may not be as informed about these noxious weeds. Ikley and his team have been busy spreading the word. 

“Last summer, we produced a video series that we’ve shown to several groups,” he says. “Last fall and winter, we presented the information to groups at meetings and trade shows. We have a 3D-printed, life-size Palmer amaranth plant that we display at these events to draw people to our booth. It is a unique way to start the conversation.”

A Palmer amaranth plant rises above a millet field in North Dakota. The millet in this field is approximately 4 to 5 feet tall and will be used for livestock feed. Photo: Joe Ikley

He has reached out to other key audiences including certified applicators, who viewed Ikley’s videos as part of their continuing education and recertification requirements. His team also exhibited at the North Dakota Stockmen’s Association’s annual conference and presented at the North Dakota Weed Control Association’s annual meeting. Ikley also created a PowerPoint presentation for agents to use in their noxious weed management trainings.

In addition, the Pigweed Awareness Campaign includes suggestions as to what can be done to reduce the infestations in a field. 

“Proper identification of Palmer amaranth is a first step, which is a point we are reinforcing,” he comments. “Then taking steps to reduce spreading it, including simple hand-pulling, if you have just a few weeds in the field. Also, test your animal feed sources. If the feed looks suspicious, there are ways to get these feed sources tested. Finally, if you know you had a contaminated feed source, manure management is important to avoid spreading it on crop fields.”

Ikley and his team are also conducting yield loss trials as well as working through the economics of controlling pigweed infestations. He hopes to continue the campaign this fall and winter to keep the pigweed awareness conversation going.

Other Resources

Pigweed Awareness Campaign video series

Identification, Biology and Control of Palmer Amaranth and Waterhemp in North Dakota – NDSU webpage

Joe Ikley profile

Published: Oct 30, 2023

The materials on SRIN were funded with checkoff dollars from United Soybean Board and the North Central Soybean Research Program. To find checkoff funded research related to this research highlight or to see other checkoff research projects, please visit the National Soybean Checkoff Research Database.